From: Luke Lonergan <llonergan@greenplum.com>
To: Worky Workerson <worky.workerson@gmail.com>
To: Craig A. James <cjames@modgraph-usa.com>
Cc: Jim C. Nasby <jim@nasby.net>
Cc: Merlin Moncure <mmoncure@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Best COPY Performance
Date: Wed, 25 Oct 2006 08:06:36 -0700
Message-ID: <C164CB8C.51BD%llonergan@greenplum.com> (raw)
In-Reply-To: <ce4072df0610250503g26f32cb7r4e668613c8665774@mail.gmail.com>
Mr. Worky Workerson,
On 10/25/06 5:03 AM, "Worky Workerson" <worky.workerson@gmail.com> wrote:
> However, I am still curious as to the rather slow COPYs from psql to
> local disks. Like I mentioned previously, I was only seeing about 5.7
> MB/s (1.8 GB / 330 seconds), where it seemed like others were doing
> substantially better. What sorts of things should I look into?
It's probable that you have a really poor performing disk configuration.
Judging from earlier results, you may only be getting 3 x 5.7 = 17 MB/s of
write performance to your disks, which is about 1/4 of a single disk drive.
Please run this test and report the time here:
1) Calculate the size of 2x memory in 8KB blocks:
# of blocks = 250,000 x memory_in_GB
Example:
250,000 x 16GB = 4,000,000 blocks
2) Benchmark the time taken to write 2x RAM sequentially to your disk:
time bash -c "dd if=/dev/zero of=bigfile bs=8k count=<# of blocks> &&
sync"
3) Benchmark the time taken to read same:
time dd if=bigfile of=/dev/null bs=8k
- Luke
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To: pgsql-performance@postgresql.org
Cc: llonergan@greenplum.com, worky.workerson@gmail.com, cjames@modgraph-usa.com, jim@nasby.net, mmoncure@gmail.com
Subject: Re: Best COPY Performance
In-Reply-To: <C164CB8C.51BD%llonergan@greenplum.com>
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